---
name: "FUTEX_WAIT_REQUEUE_PI"
section: "2const"
platform: "linux"
package: "man-pages"
version: "6.19-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/FUTEX_WAIT_REQUEUE_PI"
---

# FUTEX\_WAIT\_REQUEUE\_PI(2const)

wait on a non-PI futex, and potentially be requeued onto a PI futex

## NAME

FUTEX\_WAIT\_REQUEUE\_PI - wait on a non-PI futex, and potentially be requeued onto a PI futex

## LIBRARY

Standard C library (*libc*, *-lc*)

## SYNOPSIS

```
#include <linux/futex.h>  /* Definition of FUTEX_* constants */
#include <sys/syscall.h>  /* Definition of SYS_* constants */
#include <unistd.h>
```

**long syscall(SYS\_futex, uint32\_t \****uaddr***, FUTEX\_WAIT\_REQUEUE\_PI,**              **uint32\_t** *val***,**              **const struct timespec \****timeout***,**              **uint32\_t \****uaddr2***);**

## DESCRIPTION

Wait on a non-PI futex at *uaddr* and potentially be requeued (via a [**FUTEX\_CMP\_REQUEUE\_PI**(2const)](/FUTEX_CMP_REQUEUE_PI/2const.md) operation in another task) onto a PI futex at *uaddr2*. The wait operation on *uaddr* is the same as for [**FUTEX\_WAIT**(2const)](/FUTEX_WAIT/2const.md).

The waiter can be removed from the wait on *uaddr* without requeueing on *uaddr2* via a [**FUTEX\_WAKE**(2const)](/FUTEX_WAKE/2const.md) operation in another task. In this case, the **FUTEX\_WAIT\_REQUEUE\_PI** operation fails with the error **EAGAIN**.

If *timeout* is not NULL, the structure it points to specifies an absolute timeout for the wait operation. If *timeout* is NULL, the operation can block indefinitely.

## RETURN VALUE

On error, -1 is returned, and *errno* is set to indicate the error.

On success, **FUTEX\_WAIT\_REQUEUE\_PI** returns 0 if the caller was successfully requeued to the futex for the futex word at *uaddr2*.

## ERRORS

See [**futex**(2)](/futex/2.md).

- **EAGAIN** or **EWOULDBLOCK**

  The value pointed to by *uaddr* was not equal to the expected value *val* at the time of the call.

- **EFAULT**

  *uaddr2* or *timeout* did not point to a valid user-space address.

- **EINVAL**

  The supplied *timeout* argument was invalid (*tv\_sec* was less than zero, or *tv\_nsec* was not less than 1,000,000,000).

- **EINVAL**

  *uaddr2* does not point to a valid object—that is, the address is not four-byte-aligned.

- **ENOSYS**

  A run-time check determined that the operation is not available. The PI-futex operations are not implemented on all architectures and are not supported on some CPU variants.

- **ETIMEDOUT**

  The timeout expired before the operation completed.

## STANDARDS

Linux.

## HISTORY

Linux 2.6.31.

## SEE ALSO

[**futex**(2)](/futex/2.md)